US History. Need some input.

[Lars]

If you would need to write an essay about one point in the U.S. History
that you could change what would it be? Of course it needs to have
some interesting effects.
Please help me to find an interesting topic.

Examples:
What would have happened if George Washington would have been a women?
What would have happened if Lincoln would not have been reelected in 1864?
...

Thanks!